Vertical mail piece stacker

ABSTRACT

A mail piece stacker system includes a back wall and a side wall. A platform is mounted adjacent to the back wall and side wall and is moveable in a vertical direction. The platform is adapted to support a stack of mail pieces, such as mail pieces, and has means connected to the platform to position the platform in a first vertical position when no mail pieces are on the platform and to position the platform in a different vertical position lower than the first vertical position when mail pieces are on the platform. The platform may be positioned at an acute angle with respect to the back wall and the side wall to help in registering mail pieces being stacked on the platform. The stacker may employ the method of moving mail pieces seriatim onto a platform. The platform is moveable in a vertical direction and is moved in a downward direction as mail pieces are stacked on the platform. The movement is such that the vertical level of the stacker platform is adjusted as mail pieces are stacked on the platform so that the top surface of the topmost mail piece is substantially adjacent the vertical position of the platform when no mail pieces are on the platform.

FIELD OF THE INVENTION

The present invention relates to mail piece handling equipment and more particularly to a vertical mail piece stacker system.

BACKGROUND OF THE INVENTION

Various mail handling equipment, such as mailing machines, inserters and folders, employ mail piece stackers. Various arrangements of stackers have been implemented in mail handling equipment and also in copiers. These include auger-type stackers, drop-type stackers, and bins used to catch copy sheets in a copier output station.

In certain mail creation machines finished mail pieces are moved into a bin. Although the equipment operates satisfactorily, the employment of large bins can result in mail pieces ending up in a haphazard pile that may not preserve the order of the output of the equipment. Preserving the order the mail pieces can be important to maintain a lower postal cost for some mailings where quantity discounts are provided when mail is grouped by postal codes. Moreover, reducing the size of the bin may help in minimizing the problem of haphazard organization of the mail pieces, however, the operator must empty the bin at much more frequent intervals. Another approach has been to deposit the finished mail pieces in a horizontal conveyor (a tab-type stacker) in a shingled arrangement. While this approach tends to preserve the output order of the mail pieces and the mail is generally organized in a neat grouping, such an arrangement takes up a lot of floor space and can be very expensive. The stacking of copy sheets has been employed in copier output stations where copy sheets are moved onto a platform which is lowered by electromechanical motorized means. The platform is lowered so that the distance traveled by the copy sheets to the top of the stack is minimized.

It is desirable in media stacking systems to provide stacks that are neat, preserve the output order of the mail pieces from the media handling equipment, such as the inserters, folders and the like, and also allow unloading while the equipment is running. It is desirable in stacking systems to facilitate the unloading and to facilitate easy transport of the mail pieces from the stacker, such as in a mailing tray for mail pieces.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a flexible stacker that will not require a long drop into a single bin design and will help preserve the output order from mail pieces handling equipment in a neat stack.

It is a further object of the present invention to provide a stacker configuration that facilitates user unloading of the stacker.

It is yet another object of the present invention to provide an effective vertical stacker that takes up a small footprint and also stacks mail pieces neat enough to allow the operator to transfer the mail pieces in an ordered stacking such as to a mail piece mailing tray employed by the United States Postal Service (USPS) and other posts.

It has been discovered that a vertical, or near-vertical, stacking arrangement can be employed which can receive or catch, for example, mail pieces near a mailing machine exit and have a platform that moves in substantially vertical direction and functions as an elevator. The platform moves down to allow the next mail piece to rest on top of the previous mail piece at substantially the same position of the platform when it receives the first mail piece in a stack.

It has been discovered that the elevator-type arrangement can be organized to let the weight of the mail piece work against a spring element so that a platform continuously moves down under the weight of successive mail pieces. User adjustments can be implemented to accommodate different mail piece sizes and combinations. Alternatively, the platform can be moved down under control of a motor and a sensing system and organized to facilitate unloading requirements after which the platform would return to its top position after the mail pieces have been unloaded.

It has also been discovered that productivity of the stacker can be enhanced by eliminating the time required for the platform to return to the top position by having a continuous elevator arrangement where successive platforms, which may composed of separate platform segments, can be on an endless belt arrangement. The belts can be driven by motor or operated under the weight of mail pieces being stacked on the platform. The bins may be configured to hold a quantity of mail pieces suitable for an operator to unload. The lowest bin continues to follow the belt path and recycle to the top of the stacker. If all the bins are full, a sensor can be provided to detect this condition and stop the machine operation.

A mail piece stacker system embodying the present invention includes a back wall and a side wall. A platform is mounted to be adjacent to the back wall and the side wall. The platform is moveable in a vertical direction and is adapted to support a stack of mail pieces. A support spring is connected to the platform to position the platform in a first vertical position when no mail pieces are on the platform and to position the platform in a different lower vertical position than the first vertical position when the mail pieces are on the platform.

A method for stacking mail pieces embodying the present invention includes the steps of moving mail pieces off a machine exit seriatim onto a stacker platform. Adjusting the vertical level of the stacker such that as mail pieces are moved onto the stacker platform, the topmost mail piece surface remains at substantially the height of the platform without any mail pieces on the platform.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference is now made to the various figures, wherein like reference numerals designate similar items in the various figures and in which:

FIG. 1 is a perspective view of a mail piece stacker system embodying the present invention;

FIGS. 2-5 are diagrammatic representations of the stacker shown in FIG. 1 having different quantities of mail pieces on the stacker platform; and,

FIG. 6 is an alternative embodiment of a mail piece stacker system employing the present invention with stacker platforms connected to an endless belt arrangement.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference is now made to FIG. 1. Mail piece handling equipment shown generally at 2 includes a machine with a mail piece exit. The exit may be a mail piece conveyor 4 for conveying mail pieces from the mail piece handling equipment 2. Mail pieces are conveyed by the belts 6, 8, 10 and 12 toward a vertical stacker, generally shown at 14. The vertical stacker 14 includes a base 16 which is physically connected by brackets 18 and 20 to the mail piece handling equipment 2. This establishes a specific spatial relation between the stacker 14 and the mail piece handling equipment 2.

The stacker 14 includes a platform 22 for receiving mail pieces exiting the mail piece handling equipment 2 and conveyed by the conveyor 4 to the stacker 14. A stack of envelopes 24 is shown neatly stacked on the platform 22. The mail pieces are transported on conveyor belts 6, 8, 10 and 12. The platform 22 is connected to a vertically moveable plate 26 having a handle 28 and forming part of a back wall which includes the vertical plate 29 to which the moveable plate 26 is attached. The plate 28 is at a right angle to the side wall 30 of the stacker.

The platform 22 is positioned at an acute angle with respect to the back wall of the stacker. Additionally, the platform 22 is at an acute angle with respect to the side wall 30. In this manner, where desired and where the acute angles are such to make the slope of the platform sufficient, when a mail piece hits the back wall moveable plate 26 and settles onto the stack 24, the mail piece will tend to slide toward the side wall 30 and become registered in the stack. The side wall 30 of the stacker is perpendicular to the back wall; however, other angles may be employed. The platform 22 is oriented so that it is at a compound angle. The platform is oriented at an acute angle with respect to the back wall and plate 22 and also at an acute angle with respect to the side wall 30. Mail pieces which do not fly far enough to strike the back wall plate 26 and land on the stack tend to slide toward the back wall plate 26 and also toward the side wall 30, where they are registered in the stack. When exiting the mail piece handling equipment conveyor 4, the lead edge of the mail piece will hit the back wall plate 26 and then settle onto the stack 24. Since the stack 24 is angled due to the platform orientation, the mail piece will tend to slide against the side wall 30 to become fully registered.

A spring 31, shown diagrammatically in FIGS. 2-5 is connected to the platform 22. When no mail pieces are stacked on the platform 22, the platform 22 will assume a vertical position substantially at the position of mail piece 24 d. As mail pieces move off the conveyor they become airborne and travel toward the back wall. The mail piece will strike the back wall plate 26 and settle onto the stack. Guide bars or strips 32 and 34 help guide the portion of the mail piece trailing the lead edge of the mail piece. The angled orientation of the platform 22, and also mail pieces in the stack of mail pieces 24, facilitates the settling of the mail piece onto the stack. The spring 31 is not shown in FIG. 1. The spring 31 is directly under and hidden from view in FIG. 1 by the platform 22. Spring 31 may be a compression type spring connected to base 16 as shown in FIGS. 2-5.

A slot 36 is provided in the base 16. This enables the stacker mechanism to be moved toward and away from the end of the mail piece handling equipment conveyor 4 and the guide bars or strips 32 and 34. This enables the stacker to accommodate different width mail pieces. To facilitate unloading of the stacker, an operator may lift the stack of mail pieces 24 by the handle 28. This will raise the plate 26 and the attached platform 22 to a comfortable height for unloading. A locking mechanism 38 (shown in FIGS. 2-5) when engaged as shown in FIG. 5, locks the platform 22 in a position for unloading the stack of mail pieces 24.

The neatness of the stack of mail pieces is directly related to how far the mail piece has to travel through the air or land on a stack. With the present arrangement, as shown in the various figures, by having a small drop, for example, a 3-4 inch drop, there is a good likelihood of mail pieces stacking flat on the bin platform and with the next mail piece landing directly on top of the previous mail piece in a way that the mail piece stack is neat. The further that the landing point, the platform or the bin floor is from the place where the mail piece took off, the more likely that the mail piece will flip or have erratic movement while traveling through the air. Since the mail piece is aerodynamic and since it does have a rotational characteristic as it leaves the exit of the mail handling equipment, the further the distance the mail piece moves through the air from the leap or exit point, the more likely the mail piece is to flip or travel erratically and then not end up being neatly stacked on the platform. By always maintaining a platform catch point that is relatively close to the mail handling equipment exit point, the greater the likelihood of making a neat, organized mail piece stack.

As is illustrated in FIGS. 2-4, the stacker platform functions similar to an elevator. The platform 22, under the action of spring 31, starts with the platform 22 at a top position. As the mail pieces stack on top of the platform 22, by virtue of the weight of the stack 24, the spring 31 allows the platform 22 to move down under the weight of the growing mail piece stack but still presents a good landing point, on the top of the topmost mail piece, for the next exiting mail piece to make a neat, flat landing. This is because the topmost mail piece on the platform 22 is substantially at the position where the platform 22 was located without any mail pieces stacked thereon.

Different mail pieces may have different weights, depending on how many inserts are in the mail piece. However, the more inserts in an envelope or mail piece, the thicker the envelope or mail piece and thus the vertical position of the topmost mail piece, which is the landing point for the next mail piece, remains approximately constant for a given size envelope, regardless of the number of inserts where an appropriate spring is employed. One variable that makes the mail piece different in weight is generally the width and length of the mail piece. However, many mail pieces are of similar length. The mail piece widths often fall into two major categories for many mail creation machines. One is the number 10 envelope, about 3½ to 4 inches wide and about 9 inches long, the other is the C5 envelope, which is about 6 inches wide and 9 inches long. The spring 31 can be tuned to accommodate these different width mail pieces by either changing the spring arrangement for the different width mail pieces (adding, removing or substituting different springs or providing an adjustment mechanism) or selecting a spring 31 that is an accommodation for the different width mail pieces, such as No. 10 and/or C5 envelopes. The selection of a spring to accommodate the two width mail pieces or multiple width mail pieces is a trade-off between the settling of the platform 22 and the effort to change or tune the spring. However, a spring can be selected that satisfactorily accommodates multiple-sized mail pieces. Since the small size envelopes are less aerodynamically stable than larger size envelopes, by primarily accommodating the requirements of a No. 10 envelope, for example, a selection will be made that may still be satisfactory for a C5 size envelope.

As noted above, a mail piece that is thicker with more inserts pushes down more on the platform than a thinner envelope with fewer inserts. The landing point for the next mail piece mail, however, remains about the same regardless of whether the thicker or thinner mail piece is on the platform 22 providing the landing surface. Accordingly, whether a single insert or eight inserts are in an envelope, the landing point for the next mail piece remains at substantially the same height. A single insert makes a thinner mail piece, which weighs less, and does not depress the spring and platform as much as a thicker mail piece. Accordingly, a thinner or thicker mail piece has a change in platform height, where the topmost mail piece on the platform still remains at substantially the same height regardless of which mail piece is placed on the platform. If the mail piece is a thicker packet, it weighs more and pushes the stack down more, but still ends up with the same landing point for the next mail piece. It should be recognized that selection of the spring 31 and/or changing the spring or tuning the spring for different sized envelopes and other variables is a design choice, depending upon the particular requirements for the stacker and the media being employed.

Other important parameters in addition to the spring selection are the platform angle with respect to the back wall plate 26 and with respect to the side wall 30 and the location of the back wall with respect to the mail piece exit point of the mail handling equipment. The guides 32 and 34 may be arranged to guide mail pieces exiting the mail handling equipment onto the mail piece stack 24. The guides 32 and 34 guide portions of an envelope trailing the lead edge of an envelope as they move off the conveyor and onto the mail piece stack 24.

In general operation, mail pieces exit the mail handling equipment conveyor 4 and hit the back wall plate 26 and drop onto the stack 24. As the mail piece exits the conveyor 4, the mail piece starts to fall and the lead edge of the mail piece is angled downwardly with respect to the trail edge of the mail piece. In one configuration, the mail piece hits the back wall about an inch above where it will settle onto the platform 22 or topmost mail piece in the stack 24. The greater the settling distance, the more variation that may occur in the mail piece stack. As the mail piece exits the equipment and moves off the edge of the conveyor 4 support, it begins a rotational movement no matter how fast the mail piece moves off the edge of the equipment. The lead edge of the mail piece starts to drop once the center of gravity goes over the end of the mail piece handling equipment conveyor. At this point, the mail piece starts a rotational movement. The mail piece tends to rotate down but hits the back wall plate 26 and lands on the stack 24 before it rotates too far. Otherwise, the mail piece may end up with the lead edge going straight into the edge of the mail piece stack 24 and the mail piece, clearly, in such case will not stack properly.

The further the mail piece has to travel to get onto the stack 24, the more time exists when the rotational movement of the mail piece will continue and further travel tends to create an erratic stacking. By keeping the stacking platform 22 at a substantially stable position with limited vertical stacking height movement and also close to the mail piece exit point for all mail pieces, the rotational effect and erratic travel is minimized. Additionally, orienting the platform 22 at an angle with respect to the back-wall plate 26 further minimizes the distance the trailing edge of a mail piece has to fall to settle onto the stack. This angle mimics the approach angle of an airborne mail piece and less time is needed for the trailing edge of the mail piece to settle onto the platform 22 or the topmost envelope in the stack 24. This further tends to reduce variation in the stacking of the mail pieces.

When the platform stack is full, the platform 22 can be positioned to assist the operator in unloading the stacker 14. A platform lock 40 is provided. The platform lock 40 may include a sliding member 42 (shown in FIG. 5) which will engage the platform 22 to lock the platform into a position to facilitate operator unloading of the stacker 14. The handle 28 may be used by the operator to lift the platform and the stack of mail pieces and lock the platform for unloading. The position for unloading may be an upper position as shown in FIG. 5. However, the position to facilitate unloading is a matter of design choice based on the equipment involved and the stacking apparatus.

As illustrated in FIGS. 2-5, a series of mail pieces are being conveyed by the conveyor 4 and are about to be exited from the conveyor 4 past the guides onto the stacker platform. FIG. 3 illustrates the platform 22 with a stack of mail pieces 24. The platform 22 is at a lower vertical position under the weight of the mail piece stack 24 than the platform 22 as shown in FIG. 2 with no mail pieces. However, the top surface of the topmost mail piece on the stack 24 is at approximately the same position of the platform 22 illustrated in FIG. 2 without any mail pieces thereon. FIG. 3 additionally illustrates a mail piece as having just struck the back wall 26 and preparing to drop onto the stack.

As shown in FIG. 4, the back wall of the stacker 14 has been moved and is positioned further from the conveyor 4 to accommodate larger sized mail pieces, which are being stacked on the platform 22. A mail piece is shown as having exited the conveyor 4 and moving onto the stack of mail pieces 24 on the platform. The trail edge of the mail piece is guided by the guide 32.

A full stack 24 of mail pieces on platform 22 is illustrated in FIG. 5. The platform 22 has been moved to an unloading position. The platform 22 is locked into a position for unloading by engaging locking mechanism 40. The locking is by virtue of the platform lock sliding member 42 being moved into engagement with the underside of platform 22.

Reference is now made to FIG. 6. The mail piece stacker 44 is shown with mail pieces 46 stacked on the elevator platform 48. The elevator platform is composed of two elevator platform segments 48a and 46b. As mail pieces exit a machine, the mail pieces drop onto the topmost bin, here bin 50, which is formed by platform 48. The mail piece drops on top of the topmost mail piece that previously exited the machine and were placed in bin 50. This is similar to the arrangement shown in FIGS. 1-5 where the distance the mail pieces need to travel through the air to be placed onto the stack is controlled to avoid large distances. The bins of the stacker 44 may have a capacity of, for example, about between 10-15 mail pieces, depending upon the thicknesses of the various mail pieces. However, the capacity of the particular bin is a matter of design choice.

As a bin, such as bin 50, is full, the bin moves down and a new bin moves into position above the previous bin to continue to receive mail pieces from the machine. The new bin will be formed by platform segments 52 a and 52 b. At any time, there could be a number of bins, such as five or six bins, holding mail pieces. An operator could remove mail from any of the bins, however, the mail removal would normally be from the lowest configured bin when it is not receiving mail pieces. If the lowest bin is full, before it is rotated to begin upward travel, sensor 54 will detect this condition and stop the stacker 44 and mailing machine operation.

The bins of stacker 44 are constructed as platforms or shelves, with the particular arrangement shown in FIG. 6 having two platform segments, mounted to belts 56 a and 56 b and 58 a and 58 b to form a platform to support both sides of the mail pieces. Various types of belt arrangements and platforms and segmented platforms may be employed. The belts 56 a, 56 b, 58 a and 58 b are driven by a motor 60. The motor 60 only needs power to move the bins with mail pieces in a downward direction and empty bins in an upward direction. Accordingly, the motor 60 can be of a small size. As the lowest bin is emptied, the lowest platform segments continue to follow the belts and are recycled to the top of the stack 44.

The entire bin array can be configured to be the size to fit into a mailing tray. This would enable placing the mail tray over the bin array and tilting the stacker 44 to rotate around pivot 62 into the mail tray to allow the operator to move all the stacked mail pieces into the mail tray. The arrangement shown in FIGS. 1-5 may also be configured to employ a pivot to enable tilting of the stacker 14. The tilting of the stackers 14 or 44, as the case may be, is such that the stacked output order of the mail pieces is preserved in neat stacks when moved into a mail tray. In the case of the arrangement shown in FIGS. 1-5, the pivot would be configured to avoid conflict with the mail handling equipment 2. This can be achieved, for example, by pivoting the stacker away from the mail handling equipment 2 and then swiveling the stacker to empty the mail piece stack into the mailing tray or by moving the mail handling equipment 2.

It should be recognized that while the detailed description show stackable mail piece envelopes, the invention is suitable for use with other types of mail pieces which are stackable. Accordingly, when used herein, the term mail piece is intended to be a broad term. Other modifications can be employed in the system. Various platform and segmented platform arrangements, various types of belt or chain arrangements, various types of springs and spring configurations, back and side wall configurations and various types of locking mechanisms can all be employed with the system. Various materials can be selected for the back wall and for the guides to dampen the effect of a mail piece strike and/or to facilitate mail piece sliding. Moreover, various configurations for the stacker back wall can also be implemented. For example, the back wall can have the plate 26 recessed into the plate 29 to form a continuous single surface as opposed to being mounted on the plate 29.

While the present invention has been described in connection with what is presently considered the most practical and preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiment but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 

1. A stacker system, comprising: a back wall and a side wall; a platform adapted to support a stack of mail pieces, said platform mounted adjacent said back wall, and said side wall, said platform moveable in a vertical direction; and, a means connected to said platform to position said platform in a first vertical position when no mail pieces are on said platform and to position said platform in a different vertical position lower than the first vertical position when mail pieces are on said platform.
 2. A stacker system as defined in claim 1, wherein said platform is positioned with respect to said back wall to form an acute angle such that mail pieces on said platform tend to move toward said back wall.
 3. A stacker system as defined in claim 2, wherein said platform is positioned with respect to said side wall to form an acute angle such that mail pieces on said platform tend to move toward said sidewall.
 4. A stacker system as defined in claim 1, wherein said platform is positioned with respect to said back wall to form an acute angle and said platform is positioned with respect to said sidewall to form an acute angle such that mail pieces on said platform tend to move toward said back wall and tend to move toward said side wall.
 5. A stacker system as defined in claim 4, including guide members for guiding mail pieces onto the platform.
 6. A stacker system as defined in claim 5, wherein said first vertical position of said platform is at a height to receive mail pieces moved past the guide members and onto said platform.
 7. A stacker system as defined in claim 1, wherein said means is a spring selected such that vertical downward movement of said platform under the weight of a mail piece is a distance substantially equal to the thickness of said mail piece so that the topmost mail piece of a stack of mail pieces on said platform is substantially adjacent to said first vertical position.
 8. A stacker system as defined in claim 7, wherein said platform is positioned with respect to said back wall to form an acute angle such that mail pieces on said platform tend to move toward said back wall.
 9. A stacker system as defined in claim 7, wherein said platform is positioned with respect to said side wall to form an acute angle such that mail pieces on said platform tend to move toward said sidewall.
 10. A stacker system as defined in claim 7, wherein said platform is positioned with respect to said back wall to form an acute angle and said platform is positioned with said sidewall to form an acute angle such that mail pieces on said platform tend to move toward said back wall and tend to move toward said side wall.
 11. A stacker system as defined in claim 1, wherein said platform is mounted to a moveable belt.
 12. A stacker system as defined in claim 11, wherein said platform includes a first platform segment and a second platform segment.
 13. A stacking system as defined in claim 12, wherein said means is a motor connected to said moveable belt.
 14. A stacker system as defined in claim 1, further comprising a lock mechanism for locking said platform from vertical movement.
 15. A stacker system as defined in claim 14, further comprising a pivot connected to enable said platform to be moved for unloading a stack of mail pieces on said platform into a mailing tray.
 16. A stacker system as defined in claim 7, wherein said spring is tunable to accommodate different size mail pieces.
 17. A method for stacking mail pieces, comprising the steps of: moving mail pieces seriatim onto a vertically moveable platform; and, adjusting the vertical level of said platform such that said topmost mail piece surface remains substantially adjacent the vertical position of said platform without mail pieces on said platform.
 18. A method for stacking media items as defined in claim 17, wherein said vertically moveable platform is adjacent a back wall and moving said mail pieces includes the step of moving a lead edge of each of said mail pieces to strike said back wall and thereafter move downward toward said platform.
 19. A method for stacking mail pieces as defined in claim 18, wherein said vertically moveable platform is adjacent a side wall and moving said mail pieces includes the step of moving said mail pieces toward said side wall. 